Systems and methods for synchronizing frame timing between physical layer frame and video frame

ABSTRACT

A method implemented on a computing device including at least one processor and a storage for synchronizing video transmission with physical layer. The method includes determining a first time point corresponding to a frame header of a video frame, determining a second time point corresponding to a frame header of a physical layer frame based at least in part on the first time point, and starting transmitting the video frame at the second time point.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No.PCT/CN2017/099156, filed Aug. 25, 2017, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

This application relates to systems and methods for transmissionsynchronization, more particularly, to systems and methods forsynchronizing the frame timing between a physical layer frame and avideo frame.

BACKGROUND

Unmanned movable platform (UMP) such as unmanned aerial vehicles (UAV)have been widely used in various fields such as aerial photography,surveillance, scientific research, geological survey, and remotesensing. The maneuvering of a UAV may be controlled by a user via aground terminal. The UAV may record video data during flight andtransmit the video data to the ground terminal. The ground terminal maydisplay the video data synchronously with the recording.

In order to display the video data at the ground terminal withoutcausing lags, it is important for the UAV to reduce time delay oftransmitting the video data from the UAV to the ground terminal.

SUMMARY

According to an aspect of the present disclosure, a method forsynchronizing video transmission with physical layer is provided. Themethod may be implemented on a computing device including at least oneprocessor and a storage. The method may include determining a first timepoint corresponding to a frame header of a video frame, determining asecond time point corresponding to a frame header of a physical layerframe based at least in part on the first time point, and startingtransmitting the video frame at the second time point.

In some embodiments, the method may further include generating thephysical layer frame at the second time point.

In some embodiments, the determining a second time point correspondingto a frame header of a physical layer frame based at least in part onthe first time point may include determining the second time point basedat least in part on the first time point, and synchronizing a third timepoint corresponding to a frame header of a physical layer frame with thesecond time point, the physical layer frame corresponding to the videoframe.

In some embodiments, the method may further include compressing thevideo frame before transmitting the video frame at the second timepoint.

In some embodiments, the method may further include segmenting the videoframe into a plurality of sub-frames, and compressing data associatedwith each of the plurality of sub-frames.

In some embodiments, the determining the second time point may includedetermining a time period for compressing a sub-frame of the pluralityof sub-frames, and determining the second time point based on the firsttime point and the time period for compressing the sub-frame.

In some embodiments, the determining the second time point based on thefirst time point may include determining a time period for compressingat least a portion of the video frame, and determining the second timepoint based on the first time point and the time period.

In some embodiments, the frame header of the video frame may correspondto a frame synchronization pulse signal.

In some embodiments, the video frame may be extracted from a real-timevideo stream transmitted by a video recording device.

In some embodiments, the video frame may be extracted from a real-timevideo received at a data interface communicatively connected to a videorecording device.

In some embodiments, the method may further include obtaining a framerate of the video frame, and configuring a frame rate of the physicallayer frame based on the frame rate of the video frame.

In some embodiments, the frame rate of the physical layer frame may bean integer multiple of the frame rate of the video frame.

According to another aspect of the present disclosure, a system forsynchronizing video transmission with physical layer is provided. Thesystem may include a memory that stores one or more computer-executableinstructions, and one or more processors configured to communicate withthe memory. When executing the one or more computer-executableinstructions, the one or more processors may be directed to determine afirst time point corresponding to a frame header of a video frame,determine a second time point corresponding to a frame header of aphysical layer frame based at least in part on the first time point, andstart transmitting the video frame at the second time point.

According to another aspect of the present disclosure, a non-transitorycomputer readable medium is provided. The non-transitory computerreadable medium may include executable instructions. When the executableinstructions are executed by at least one processor, the executableinstructions may cause the at least one processor to effectuate amethod. The method may include determining a first time pointcorresponding to a frame header of a video frame, determining a secondtime point corresponding to a frame header of a physical layer framebased at least in part on the first time point, and startingtransmitting the video frame at the second time point.

According to another aspect of the present disclosure, an unmannedaerial vehicle (UAV) is provided. The UAV may include at least one videorecording device, at least one processor and at least one UAVtransceiver. The at least one video recording device may be configuredto record video data including a plurality of video frames. The at leastone processor may be configured to determine a first time pointcorresponding to a frame header of a video frame of the plurality ofvideo frames, and determine a second time point corresponding to a frameheader of a physical layer frame based at least in part on the firsttime point. The at least one UAV transceiver may be configured to starttransmitting the video frame at the second time point.

Additional features will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the artupon examination of the following and the accompanying drawings or maybe learned by production or operation of the examples. The features ofthe present disclosure may be realized and attained by practice or useof various aspects of the methodologies, instrumentalities andcombinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. These embodiments are non-limiting exemplaryembodiments, in which like reference numerals represent similarstructures throughout the several views of the drawings, and wherein:

FIG. 1 illustrates a schematic diagram of an exemplary unmanned aerialvehicle (UAV) system according to some embodiments of the presentdisclosure;

FIG. 2 illustrates a block diagram of an exemplary unmanned aerialvehicle (UAV) according to some embodiments of the present disclosure;

FIG. 3 illustrates a flowchart of an exemplary process for videotransmission in a UAV system according to some embodiments of thepresent disclosure;

FIG. 4 illustrates a block diagram of an exemplary ground terminal in aUAV system according to some embodiments of the present disclosure;

FIG. 5 illustrates a block diagram of an exemplary processor in a UAVsystem according to some embodiments of the present disclosure;

FIG. 6 illustrates a flowchart of an exemplary process for transmittinga video frame in a UAV system according to some embodiments of thepresent disclosure;

FIG. 7 illustrates a flowchart of an exemplary process for configuring aframe rate of physical layer frames in a UAV system according to someembodiments of the present disclosure;

FIG. 8A and FIG. 8B illustrate two schematic diagrams of a videotransmission in a UAV system according to some embodiments of thepresent disclosure; and

FIG. 9 illustrates a schematic diagram of an exemplary open systemsinterconnection (OSI) model.

DETAILED DESCRIPTION

In the following detailed description, numerous specific details are setforth by way of examples in order to provide a thorough understanding ofthe relevant disclosure. However, it should be apparent to those skilledin the art that the present disclosure may be practiced without suchdetails. In other instances, well known methods, procedures, systems,components, and/or circuitry have been described at a relativelyhigh-level, without detail, in order to avoid unnecessarily obscuringaspects of the present disclosure. Various modifications to thedisclosed embodiments will be readily apparent to those skilled in theart, and the general principles defined herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the present disclosure. Thus, the present disclosure is not limitedto the embodiments shown, but to be accorded the widest scope consistentwith the claims.

It will be understood that the term “system,” “unit,” “module,” and/or“engine” used herein are one method to distinguish different components,elements, parts, section or assembly of different level in ascendingorder. However, the terms may be displaced by other expression if theymay achieve the same purpose.

It will be understood that when a unit, module or engine is referred toas being “on,” “connected to” or “coupled to” another unit, module, orengine, it may be directly on, connected or coupled to, or communicatewith the other unit, module, or engine, or an intervening unit, module,or engine may be present, unless the context clearly indicatesotherwise. As used herein, the term “and/or” includes any and allcombinations of one or more of the associated listed items.

The terminology used herein is for the purposes of describing particularexamples and embodiments only, and is not intended to be limiting. Asused herein, the singular forms “a,” “an,” and “the” may be intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “include,”and/or “comprise,” when used in this disclosure, specify the presence ofintegers, devices, behaviors, stated features, steps, elements,operations, and/or components, but do not exclude the presence oraddition of one or more other integers, devices, behaviors, features,steps, elements, operations, components, and/or groups thereof.

The present disclosure provides systems and methods for videotransmission synchronization in a UAV system. The present disclosureadjusts a frame timing of a physical layer transmission according toframe timing of a video stream transmission. The video stream may bereceived directly from a video recording device carried on a UAV or at adata interface communicatively connected to a video recording devicecarried on the UAV. By synchronizing the frame timings between aphysical layer frame and a video frame, the transmission delay of thevideo stream from a UAV to a ground terminal due to the wait timeassociated with each video frame may be reduced. Further, the presentdisclosure configures the frame rate of the physical layer frame to bean integer multiple of the frame rate of the video frame. Therefore, thenumber of adjustments of the frame timing during the video streamtransmission between a UAV and a ground terminal may be reduced.

FIG. 1 illustrates a schematic diagram of an exemplary unmanned aerialvehicle (UAV) system 100 according to some embodiments of the presentdisclosure. The UAV system 100 may include a UAV 102, a ground terminal104, a network 106, a server 108, and a storage 110.

The UAV 102 may be configured to collect data and transmit the collecteddata to the ground terminal 104 and/or the server 108 during flight. Thedata may include the flight status of the UAV 102, the battery usage ofthe UAV 102, information associated with the surrounding environment,etc. The data may further include text data, video data, audio data,etc. The video data may include videos, images, graphs, animations,audios, etc. The UAV 102 may transmit the data to the ground terminal104 during flight to synchronously display the content of the data onthe ground terminal 104.

The UAV 102 may be operated completely autonomously (e.g., by acomputing system such as an onboard controller), semi-autonomously, ormanually (e.g., by a user operating a control application implemented ona mobile device). In some embodiments, the UAV 102 may be operated by auser via the ground terminal 104. The UAV 102 may receive commands froman entity (e.g., human user or autonomous control system) and respond tosuch commands by performing one or more actions. For example, the UAV102 may be controlled to take off from the ground, move in the air, moveto target location or to a sequence of target locations, hover in theair, land on the ground, etc. As another example, the UAV 102 may becontrolled to move at a specified velocity and/or acceleration or alonga specified route in the air. Further, the commands may be used tocontrol one or more UAV 102 components described in FIG. 2 (e.g., videorecording device 206, sensor 210, flight controller 208, etc.). Forexample, some commands may be used to control the position, orientation,and/or operation of the video recording device 206.

The ground terminal 104 may be configured to transmit, receive, output,display, and/or process information. For example, the ground terminal104 may receive information from the UAV 102, the network 106, theserver 108, the storage 110, etc. As another example, the groundterminal 104 may transmit a command generated by a user to control theUAV 102. The command may include information to control the velocity,acceleration, altitude, and/or orientation of the UAV 102. As stillanother example, the ground terminal 104 may display images or playvideos taken by the UAV 102 to a user. As still another example, theground terminal 104 may process information received from the server 108to update the application installed on the ground terminal 104.

In some embodiments, the ground terminal 104 may include a desktopcomputer, a mobile device, a laptop computer, a tablet computer, or thelike, or any combination thereof. In some embodiments, the mobile devicemay include a smart home device, a wearable device, a smart mobiledevice, a virtual reality device, an augmented reality device, or thelike, or any combination thereof. In some embodiments, the smart homedevice may include a smart lighting device, a smart television, a smartvideo camera, an interphone, or the like, or any combination thereof. Insome embodiments, the wearable device may include a smart bracelet, asmart footgear, a smart glass, a smart watch, a smart helmet, smartclothing, a smart backpack, a smart accessory, or the like, or anycombination thereof. In some embodiments, the smart mobile device mayinclude a smartphone, a gaming device, a navigation device, a point ofsale (POS) device, or the like, or any combination thereof.

The network 106 may be configured to facilitate exchange of information.In some embodiments, one or more components in the UAV system 100 (e.g.,the UAV 102, the ground terminal 104, the server 108 and the storage110) may send information to other components in the UAV system 100 viathe network 106. For example, the ground terminal 104 may receive videosand/or images from the UAV 102 via the network 106. In some embodiments,the network 106 may be any type of a wired or wireless network, or acombination thereof. Merely by way of example, the network 106 mayinclude a cable network, a wire line network, an optical fiber network,a telecommunication network, an intranet, an Internet, a local areanetwork (LAN), a wide area network (WAN), a wireless local area network(WLAN), a metropolitan area network (MAN), a wide area network (WAN), apublic telephone switched network (PSTN), a Bluetooth® network, aZigBee® network, a near field communication (NFC) network, or the like,or any combination thereof. In some embodiments, the network 106 mayinclude wired or wireless network access points such as base stationsand/or internet exchange points (not shown), through which one or morecomponents of the UAV system 100 may be connected to the network 106 toexchange information. In some embodiments, the base stations and/orinternet exchange points may be a Wi-Fi station. In some embodiments,the UAV and/or the ground terminal 104 may access to the network 106through a competition-based random access manner or anon-competition-based random access manner.

The server 108 may be configured to process data. The data may bereceived from the UAV 102, the ground terminal 104, the network 106, thestorage 110, etc. For example, the server 108 may archive the flight loginformation from the UAV 102 in the storage 110. As another example, theserver 108 may back up information from the ground terminal 104 in thestorage 110. The server 108 may include a central processing unit (CPU),an application-specific integrated circuit (ASIC), anapplication-specific instruction-set processor (ASIP), a graphicsprocessing unit (GPU), a physics processing unit (PPU), a digital signalprocessor (DSP), a field programmable gate array (FPGA), a programmablelogic device (PLD), a controller, a microcontroller unit, a reducedinstruction-set computer (RISC), a microprocessor, or the like, or anycombination thereof. In some embodiments, the server 108 may beintegrated in the ground terminal 104.

The storage 110 may be configured to acquire and/or store information.The information may be received from components of the UAV system 100(e.g., the UAV 102, the ground terminal 104, or the server 108, etc.).For example, the storage 110 may acquire information from the groundterminal 104. In some embodiments, the information acquired and/orstored in the storage 110 may include programs, software, algorithms,functions, files, parameters, data, texts, numbers, images, or the like,or any combination thereof. For example, the storage 110 may storeimages collected by the UAV 102. As another example, the storage 110 maystore parameters (e.g., latitude, longitude, altitude of the UAV 102)from the ground terminal 104. In some embodiments, the storage 110 mayinclude a mass storage, a removable storage, a volatile read-and-writememory, a read-only memory (ROM), or the like, or any combinationthereof. In some embodiments, the storage 110 may be implemented on acloud platform including a private cloud, a public cloud, a hybridcloud, a community cloud, a distributed cloud, an inter-cloud, amulti-cloud, or the like, or any combination thereof.

It should be noted that the above description of the UAV system 100 ismerely provided for the purpose of illustration, and is not intended tolimit the scope of the present disclosure. For persons having ordinaryskills in the art, multiple variations or modifications may be madeunder the teachings of the present disclosure. For example, the UAV 102may be any type of remote device that records and transmits video data,including but is not limited to a monitoring device, a wireless sensingnetwork device, a smart home device, an onboard video device, etc.However, these variations and modifications may not depart from thescope of the present disclosure.

FIG. 2 illustrates a block diagram of an exemplary unmanned aerialvehicle (UAV) 102 according to some embodiments of the presentdisclosure. The UAV 102 may include an UAV transceiver 202, a processor204, a video recording device 206, a flight controller 208, a sensor210, an inertial measurement unit (IMU) 212, and storage medium 214.

The UAV transceiver 202 may transmit and/or receive data. The data mayinclude text, videos, images, audios, animations, graphs, or the like,or any combination thereof. In some embodiments, the UAV 102 maycommunicate with the ground terminal 104 via the UAV transceiver 202.For example, the UAV transceiver 202 may transmit a video processed bythe processor 204 to the ground terminal 104, for example, thecompressed video. As another example, the UAV transceiver 202 mayreceive commands from the ground terminal 104 to maneuver the motion ofthe UAV 102. The UAV transceiver 202 may be any type of transceiver. Forexample, the UAV transceiver 202 may be a radio frequency (RF)transceiver that is capable of transmitting or receiving data through awireless network. More particularly, the wireless network may operate invarious frequency bands, such as 433 MHz, 900 MHz, 2.4 GHz, 5 GHz, 5.8GHz, etc. In some embodiments, the UAV transceiver 202 may include atransmitter and a receiver. The transmitter and the receiver may eachimplement part or all of the functions of the UAV transceiver 202.

The processor 204 may process data. The data may be received from othercomponents of the UAV 102 (e.g., the UAV transceiver 202, the videorecording device 206, or the storage medium 214, etc.). For example, theprocessor 204 may process data received by the UAV transceiver 202. Asanother example, the processor 204 may process data to be transmitted tothe ground terminal 104 via the UAV transceiver 202. As still anotherexample, the processor 204 may receive video data from the videorecording device 206. The processor 204 may compress the video data,adjust the video data and transmit the adjusted video data to the groundterminal 104 via the UAV transceiver 202. The adjustment may includesynchronizing the transmission of the video data with physical layer.The processor 204 may receive data from the sensor 210, the flightcontroller 208, and the IMU 212 to evaluate the status of the UAV 102and determine a course of action. For example, the processor 204 mayconstantly and/or periodically communicate with the IMU 212, which maymeasure the UAV 102's velocity and attitude data, and adaptively adjustthe position of the UAV 102. In some embodiments, the processor 204 mayinclude one or more processors (e.g., single-core processors ormulti-core processors). In some embodiments, the processor 204 mayinclude a central processing unit (CPU), an application-specificintegrated circuit (ASIC), an application-specific instruction-setprocessor (ASIP), a graphics processing unit (GPU), a physics processingunit (PPU), a digital signal processor (DSP), a field programmable gatearray (FPGA), a programmable logic device (PLD), a controller, amicrocontroller unit, a reduced instruction-set computer (RISC), amicroprocessor, or the like, or any combination thereof.

The video recording device 206 may capture video data. The video datamay include images, videos, audios, graphs, animations, etc. The videorecording device 206 may be a camera, a vidicon, a video recorder, adigital camera, an infrared camera, or an ultraviolet camera, etc. Thevideo recording device 206 may send the captured video data to theprocessor 204 for processing. For example, the video recording device206 may send the captured video data to the processor 204. The processor204 may compress the video data and cause transmission of the compressedvideo data to the ground terminal 104. The ground terminal 104 mayreceive and decompress the video data. In some embodiments, the UAV 102may include a holder/pan-tilt device (not shown in FIG. 2) for mountingand/or stabilizing the video recording device 206, for example, a gimbalwith at least one axis. The processor 204 may control the operation ofthe holder/pan-tilt device to adjust the position of the video recordingdevice 206.

The flight controller 208 may control propulsion of the UAV 102 tocontrol the pitch angle, roll angle, and/or yaw angle of the UAV 102.The flight controller 208 may alter the speed, orientation and/orposition of the UAV 102. For example, upon receiving data from theground terminal 104 including a user-defined route plan, the processor204 may interpret the data and send corresponding instructions to theflight controller 208. The flight controller 208 may alter the speedand/or position of the UAV 102 based on the instructions.

The sensor 210 may collect relevant data. The relevant data may includeinformation relating to the UAV status, the surrounding environment, orthe objects within the environment. The sensor 210 may include alocation sensor (e.g., a global positioning satellite (GPS) sensor, amobile device transmitter enabling location triangulation), a visionsensor (e.g., an imaging device capable of detecting visible, infrared,or ultraviolet light, such as a camera), a proximity or range sensor(e.g., an ultrasonic sensor, LIDAR (Light Detection and Ranging), atime-of-flight or depth camera), an inertial sensor (e.g., anaccelerometer, a gyroscope, an inertial measurement unit (IMU)), analtitude sensor, an attitude sensor (e.g., a compass, an IMU), apressure sensor (e.g., a barometer), an audio sensor (e.g., amicrophone), a field sensor (e.g., a magnetometer, an electromagneticsensor), or the like, or any combination thereof. Data collected by thesensor 210 may be sent to the processor 204.

The IMU 212 may measure an angular velocity (e.g., attitude change) anda linear acceleration (e.g., velocity change) of the UAV 102. Forexample, the IMU 212 may include one or more gyroscopes to measureattitude change (e.g., absolute or relative pitch angle, roll angle,and/or yaw angle) of the UAV, and may include one or more accelerometersto measure linear velocity change (e.g., acceleration along x, y, and/orz directions) of the UAV 102. In some embodiments, the IMU 212 may beintegrated in the sensor 210.

The storage medium 214 may store data. The data may be obtained from theUAV transceiver 202, the processor 204, the video recording device 206,the flight controller 208, the sensor 210, the IMU 212, and/or any otherdevices. The data may include image data, video data, metadataassociated with the image data and the video data, instruction data,etc. The storage medium 214 may include a hard disk drive, a solid-statedrive, a removable storage drive (e.g., a flash memory disk drive, anoptical disk drive, etc.), a digital video recorder, or the like, or anycombination thereof.

It should be noted that the above description of the UAV 102 is merelyprovided for the purposes of illustration, and is not intended to limitthe scope of the present disclosure. For persons having ordinary skillsin the art, multiple variations or modifications may be made under theteachings of the present disclosure. For example, some other componentsmay be implemented in the UAV 102, e.g. a battery may be implemented inthe UAV 102 as a power supply. As another example, the UAV 102 mayinclude an electronic speed controller (ESC) for controlling oradjusting the rotation speed of motors mounted therein. However, thosevariations and modifications may not depart from the scope of thepresent disclosure.

FIG. 3 illustrates a flowchart of an exemplary process 300 for videotransmission in a UAV system according to some embodiments of thepresent disclosure. In some embodiment, the exemplary process 300 may beimplemented by one or more processors of the UAV 102.

In step 302, video data may be recorded. In some embodiments, step 302may be implemented by the video recording device 206 (illustrated inFIG. 2). The video data may include videos, audios, images, graphs,animations, or the like, or any combination thereof. In someembodiments, the video data may include a plurality of video frames. Insome embodiments, step 302 may be performed in response to a requestreceived from the processor 204 or the ground terminal 104. For example,a user of the ground terminal 104 may send a request for recording videodata via a user interface (e.g., the user interface 408 illustrated inFIG. 4). Upon receiving the request, the video recording device 206 maybe activated to record the video data. As another example, commands torecord the video data may be pre-programmed by the user via groundterminal 104 and stored in storage medium 214 of the UAV 102. Therecording of the video data may be controlled by the processor 204 viaexecuting the pre-programmed commands stored in the storage medium 214.

In step 304, a video frame may be extracted from the video data. In someembodiments, step 304 may be implemented by the processor 204. As usedherein, the video frame may refer to a frame of the video data. Thevideo frame may correspond to a length of time depending on thecompressing algorithms. In some embodiments, the video frame may be astill image. The video frame may include a frame header. The frameheader may indicate the start of the video frame transmission. The frameheader may include information of the video frame, such assynchronization information, address information, error controlinformation, coding information, etc. The synchronization informationmay include a start time point and/or an end time point of the videoframe. In some embodiments, the frame header may correspond to a framesynchronization pulse signal. The frame synchronization pulse signal mayindicate the start time point of the video frame. In some embodiments,the video frame may be segmented into a plurality of sub-frames. Dataassociated with each of the plurality of sub-frames may be compressedand/or packed into a data package for transmission. Each of theplurality of sub-frames may correspond to a portion of the video frame.The lengths of the segmented sub-frames may be the same or different.

In step 306, transmission of a physical layer frame may be synchronizedwith transmission of the video frame over the physical layer. In someembodiments, step 306 may be implemented by the processor 204. In anopen system interconnection (OSI) architecture, the physical layerdefines the means of transmitting raw bits over a physical linkconnecting network nodes. The bit stream may be converted to a physicalsignal to be transmitted over a hardware transmission medium. Thephysical layer comprises a physical signaling sublayer that interfaceswith the data link layer's media access control (MAC) sublayer andperforms signaling control of transmission and reception. The physicallayer frame according to the present application refers to a framegenerated by the physical layer of the OSI architecture that performssignaling control of transmission and reception via the physical layer.The transmission of a data package (e.g., a compressed and/or packedvideo frame or sub-frame thereof) through the physical layer iscontrolled by a physical layer frame. In particular, transmission of thefirst bit of the physical layer frame may signal the allowability oftransmitting the first bit of the data package (e.g., compressed and/orpacked video frame or sub-frame thereof). That is, the timing oftransmitting the first bit of the data package (also referred to asframe timing of the video frame) needs to be synchronous to the timingof transmitting the first bit of the physical layer frame (also referredto as frame timing of the physical layer frame). When the frame timingof the video frame is asynchronous to the frame timing of the physicallayer frame, the video frame may not be transmitted immediately. When itis determined that the frame timing of the video frame is synchronous toa frame timing of one of the succeeding physical layer frames from thecurrent physical layer frame, transmission of the video frame throughthe physical layer may be allowed. As the UAV 102 may access the network106 in a non-competition-based random access scheme, the physical layerframe for transmission control may be generated in a random basis. Insome embodiments, the physical layer frames may be generated inaccordance to a scheduling of a timer of the physical layer. The frametiming of the physical layer frame and the frame timing of the videoframe may be asynchronous. As a result, the start of the physical layerframe transmission (also referred to as the frame header of physicallayer frame) and the start of the video frame transmission (alsoreferred to as a time point that a compressed and/or packed sub-framecan be transmitted) through the physical layer may be asynchronous. Forexample, when a sub-frame of the video frame is compressed and/or packedinto a data package and ready to be transmitted in the physical layer,the expected transmission starting time may fall in the middle oftransmission of a physical layer frame. The compressed sub-frame, i.e.,the data package, may have to wait for a period of time (also referredto as a wait time) before being transmitted and thus, causing atransmission delay. As the physical layer frame for transmission controlmay be generated in a random basis or in accordance to the scheduling ofthe timer of the physical layer, the wait time before a data package isallowed to transmit is unpredictable. In order to reduce the wait timebefore transmission of the data package, the frame header of thephysical layer frame may be adjusted. For example, the time pointcorresponding to the frame header of the physical layer frame may beadjusted to be synchronized with the time point at which the compressedand/or packed sub-frames are expected to transmit. Detailed process ofthe synchronization may be found elsewhere in the present disclosure(e.g., in the description of FIG. 6, FIG. 8A, FIG. 8B, etc.).

In step 308, the video frame may be transmitted. In some embodiments,step 308 may be implemented by the processor 204. The video frame may besent to one or more other components of the UAV 102, such as the UAVtransceiver 202, the storage medium 214, etc. For example, the videoframe may be sent to the UAV transceiver 202 for processing. Theprocessing may include amplification, analog-to-digital conversion,digital-to-analog conversion, etc. The UAV transceiver 202 may send theprocessed data to the ground terminal 104. As another example, the videoframe may be stored in the storage medium 214. In some embodiments, thevideo frame may be transmitted in a physical layer. As described in step306, the physical layer frame may be synchronized with the video frameso that the time point when the video frame (or a compressed and/orpacked sub-frame thereof) can be transmitted is synchronized with theframe header of the physical layer frame. The video frame (or thecompressed and/or packed sub-frames thereof) may be transmitted with thephysical layer frame in the physical layer.

It should be note that the steps as shown in FIG. 3 are for illustrativepurpose, and are not intended to limit the protection scope of thepresent disclosure. In some embodiments, the process 300 may beaccomplished with one or more additional steps not described, and/orwithout one or more the steps discussed above. Additionally, the orderthat the steps of the process 300 are performed in FIG. 3 is notintended to be limiting. For example, one or more other optional stepsmay be added between any two steps in the process illustrated in FIG. 3.Examples of such steps may include storing or caching the video data, orthe like.

FIG. 4 illustrates a block diagram of an exemplary ground terminal 104in a UAV system according to some embodiments of the present disclosure.The ground terminal 104 may include a ground terminal transceiver 402, aprocessor 404, a display 406, a user interface 408, and a memory 410.

The ground terminal transceiver 402 may transmit and/or receive data.The data may include text, videos, images, audios, animations, graphs,or the like, or any combination thereof. In some embodiments, the groundterminal 104 may communicate with the UAV 102 via the ground terminaltransceiver 402. For example, the ground terminal transceiver 402 maytransmit an instruction (e.g., an instruction to record video data) fromthe processor 404 to the UAV transceiver 202. Upon receiving theinstruction from the ground terminal 104, the UAV transceiver 202 maysend the instruction to the video recording device to start recordingvideo data. The ground terminal transceiver 402 may be any type oftransceiver. For example, the ground terminal transceiver 402 may be aradio frequency (RF) transceiver that is capable of transmitting orreceiving data over a wireless network. More particularly, the wirelessnetwork may operate in various frequency bands, such as 433 MHz, 900MHz, 2.4 GHz, 5 GHz, 5.8 GHz, etc. In some embodiments, the groundterminal transceiver 402 may include a transmitter and a receiver. Thetransmitter and the receiver may each implement part or all functions ofthe ground terminal receiver 402.

The processor 404 may process data. The data may be received from theground terminal transceiver 402, the memory 410, etc. The data mayinclude information relating to the state of the UAV 102 (e.g.,velocity, acceleration, altitude, etc.), image data, video data, a userinstruction (e.g., an instruction to increase altitude of the UAV 102),etc. In some embodiments, the processing of the data may includestoring, classifying, selecting, transforming, calculating, estimating,encoding, decoding, or the like, or any combination thereof. Forexample, the processor 404 may decompress a compressed video framereceived from the UAV 102. As another example, the ground terminal 104may receive an application updating package from the server 108 via theground terminal transceiver 402. The processor 404 may process theapplication updating package to update the related mobile applicationinstalled on the ground terminal 104. As still another example, theprocessor 404 may process data from the memory 410 to view thehistorical flight logs. In some embodiments, the processor 404 mayinclude one or more microprocessors, filed programmable gate arrays(FPGAs), central processing units (CPUs), digital signal processors(DSPs), etc.

The display 406 may display information. The information may includetext, audios, videos, images, or the like, or any combination thereof.The display 406 may include a liquid crystal display (LCD), a lightemitting diode (LED)-based display, a flat panel display or curvedscreen, a television device, a cathode ray tube (CRT), or the like, or acombination thereof. In some embodiments, the display 406 may include atouchscreen. In some embodiments, the information displayed on thedisplay 406 may relate to the status of the UAV 102, such as altitude,velocity, etc. In some embodiments, images and/or videos captured by thevideo recording device 206 may be displayed on the display 406.

The user interface 408 may receive user interactions with the groundterminal 104 and generate one or more instructions to operate one ormore components of the ground terminal 104 or other components in theUAV system 100. The one or more instructions may include an instructionto operate the ground terminal transceiver 402 to communicate with theUAV transceiver 202, an instruction to operate the processor 404 toprocess data received from the ground terminal transceiver 402, aninstruction to operate the display 406 to display images and/or videosreceived, an instruction to operate the memory 410 to store data, aninstruction operate the UAV 102 to capture video data, or the like, orany combination thereof. In some embodiments, the user interface 408 mayinclude one or more input devices, such as a touchscreen, a keyboard, amouse, a trackball, a joystick, a stylus, an audio recognition device orapplication, etc. For example, a keyboard may be integrated in theground terminal 104. An instruction may be generated in response topressing down a plurality of keys on the keyboard in a certain sequenceby a user. In some embodiments, the instruction may direct the UAV 102to adjust flight attitudes. In some embodiments, the instruction maydirect the video recording device 206 to take a photo or to record avideo. In some embodiments, the instruction may direct the display 406to display the photo or the video. In some embodiments, the instructionmay direct the memory 410 to store data. For example, after a video isobtained, the memory 410 may receive an instruction to store the video.

The memory 410 may store data. The data may be obtained from the groundterminal transceiver 402, the processor 404, the display 406, the userinterface 408, and/or any other components in the UAV system 100. Thedata may include image data, video data, metadata associated with theimage data and the video data, instruction data, etc. In someembodiments, the memory 410 may include a hard disk drive, a solid-statedrive, a removable storage drive (e.g., a flash memory disk drive, anoptical disk drive, etc.), a digital video recorder, or the like, or acombination thereof.

It should be noted that the above description of the ground terminal 104is merely provided for the purposes of illustration, and is not intendedto limit the scope of the present disclosure. For persons havingordinary skills in the art, multiple variations or modifications may bemade under the teachings of the present disclosure. For example, one ormore components of the ground terminal 104 may include an independentstorage block (not shown) respectively. However, those variations andmodifications may not depart from the scope of the present disclosure.

FIG. 5 illustrates a block diagram of an exemplary processor 204 in aUAV system according to some embodiments of the present disclosure. Theprocessor 204 may include a data acquisition module 502, a datacompressing and packing module 504, a physical layer processing module506, and a storage module 508. The modules in the processor 204 may beconnected in a wired or wireless manner.

The data acquisition module 502 may obtain data. The data may relate tothe UAV 102 (e.g., velocity of the UAV 102), the surrounding environment(e.g., temperature, barometric pressure, etc.), or objects within theenvironment. The data may include image data, audio data, video data, orthe like, or any combination thereof. The data may be obtained from theUAV transceiver 202, the video recording device 206, the storage medium214, or other components of the UAV system 100. In some embodiments, thevideo data may include a real-time video stream. The real-time videostream may be transmitted by the video recording device 206, or receivedat a data interface communicatively connected to the video recordingdevice 206. The video data may include a plurality of video frames. Eachof the plurality of video frames may have a frame header. The frameheader of each of the plurality of video frames may correspond to aframe synchronization pulse signal. The frame synchronization pulsesignal may indicate a start time point of transmitting the each of theplurality of video frames in the physical layer.

The data compressing and packing module 504 may compress and/or packdata. The data may be received from the data acquisition module 502, orthe storage module 508. The data compressing and packing module 504 maybe configured to reduce the redundancy in the data. The redundancy mayinclude temporal redundancy, spatial redundancy, statistical redundancy,perceptual redundancy, etc. The data may be compressed in variouscompression algorithms. The compression algorithms may include losslessdata compression, and lossy data compression. The lossless datacompression may include run-length encoding (RLE), Lempel-Zivcompression, Huffman coding, prediction by partial matching (PPM), bzip2compression, or the like, or any combination thereof. The lossy datacompression may include fractal compression, vector quantization,wavelet compression, linear predictive coding, or the like, or anycombination thereof. In some embodiments, the data may be video data.The video data may be compressed under a video coding standard. Thevideo coding standard may include but not limited to H.120, H.261,H.262, H.263, H.264, high efficiency video coding, MPEG-4, or the like,or any combination thereof.

In some embodiments, the data compressing and packing module 504 mayalso be configured to pack the compressed data. For example, thecompressed data may be packed in various formats. Exemplary packagingformats may include an AVI format, a DV-AVI format, a WMV format, a MP4format, a RMVB format, a MOV format, a FLV format, or the like, or anycombination thereof. In some embodiments, the compressed data may bepacked into a data package that complies with the physical layerprotocols.

As described elsewhere in the present disclosure, a video frame may besegmented into a plurality of sub-frames of the same or differentlengths. Each of the plurality of sub-frames may correspond to a portionof the video frame. The data compressing and packing module 504 maycompress data associated with the each of the plurality of sub-frames.Alternatively or additionally, the compression and packing module 504may further pack the compressed data.

The physical layer processing module 506 may be configured to processdata. The data may be obtained from the data acquisition module 502 orthe data compressing and packing module 504. In some embodiments, theprocessing of the data may include extracting a frame header from avideo frame, determining a time point and/or a time period,synchronizing two or more time points, or the like, or any combinationthereof. For example, a video frame may be acquired by the dataacquisition module 502 from the video recording device 206. A sub-frameof the video frame may then be compressed and/or packed by the datacompressing and packing module 504. The compressed and/or packedsub-frame may be transmitted in the physical layer. A physical layerframe may control the data transmission (including the transmission ofthe compressed and/or packed sub-frame) in the physical layer. A frameheader of the physical layer frame which corresponds to a time point atwhich the data transmission starts may be determined. However, the startof the physical layer frame transmission (or referred to as the frameheader of physical layer frame) and the start of the video frametransmission (or referred to as a time point that a compressed and/orpacked sub-frame can be transmitted) may be asynchronous. Therefore, thesub-frame may have to wait for a period of time (also referred to as await time) before being transmitted and a delay may be caused. In orderto reduce the wait time and delay, the frame header of the physicallayer frame may be adjusted. For example, the time point correspondingto the frame header of the physical layer frame may be adjusted to besynchronized with the time point at which the compressed and/or packedsub-frames can be transmitted. Detailed process of the synchronizationmay be found in, for example, FIG. 6 and the description thereof.

The physical layer processing module 506 may include a timedetermination unit 510, a time adjustment unit 520, and a datatransmitting and receiving unit 530.

The time determination unit 510 may be configured to determine a timepoint and/or a time period. The time point may correspond to a frameheader of a video frame, or a frame header of a physical layer frame.The time point may also include a time point that the compression and/orpacking of the video frame is started or completed, a time point thatthe compression and/or packing of the sub-frame of the video frame isstarted or completed, a time point that a camera (e.g., the videorecording device 206) starts to record video data, etc. In someembodiments, the time point may be determined based on a signal. Forexample, the frame header of the video frame may correspond to a framesynchronization pulse signal. The time point corresponding to the frameheader of the video frame may be determined based on the framesynchronization pulse signal. As another example, the frame header ofthe physical layer frame may correspond to a physical layer pulsesignal. The time point corresponding to the frame header of the physicallayer frame may be determined based on the physical layer pulse signal.Merely by way of example, the frame synchronization pulse signal mayindicate a time point of receiving the video frame from the videorecording device.

The time period may include a time period for compressing and/or packingthe video frame, a time period for compressing and/or packing thesub-frame of the video frame, a time period for transmitting thephysical layer frame (and/or the compressed and packed sub-frames), or atime period that the processor 204 operates, etc. In some embodiments,the time period of compressing and/or packing the video frame (orsub-frames thereof) may be determined based on the length of the videoframe and the compression and/or packing algorithms used. In someembodiments, the time determination unit 510 may be implemented by atimer. The timer may be a counter that provides an internal reading. Thereading may rise in every fixed time period (e.g., a microsecond, amillisecond, a second, etc.). In some embodiments, when the readingreaches a preset number, the timer may generate a signal and the readingmay be zeroed. In some other embodiments, the timer may generate asignal periodically without zeroing its reading. For example, the signalis generated when the reading is a multiple of 100. In some embodiments,the timer may record its internal reading when a frame synchronizationpulse signal is detected (e.g., at a time point corresponding to theframe header of the video frame). In some embodiments, the timer mayrecord the time period (or a number increase in its internal reading) ofcompressing and/or packing the sub-frame.

The time adjustment unit 520 may be configured to adjust the time pointand/or time period determined by the time determination unit 510. Forexample, the time adjustment unit 520 may adjust the time pointcorresponding to the frame header of the physical layer frame. Moreparticularly, the time point may be adjusted such that the time pointcorresponding to the frame header of the physical layer frame may besynchronized with a time point when the compressed and/or packedsub-frames are ready to be transmitted. The compressed and/or packedsub-frame may be transmitted with the physical layer frame in thephysical layer. In some embodiments, the period of time of a presentphysical layer frame may be extended or shorten such that the frameheader of the succeeding physical layer frame is synchronized with thesub-frame to be transmitted. In some other embodiments, internal readingof the timer may control the frame header of the physical layer frame.For example, a physical layer frame is generated when the reading of thetimer reaches a certain value. By changing the readings of the timer,the frame header of the physical layer frame may be shifted such thatthe frame header of the succeeding physical layer frame is synchronizedwith the time point that the sub-frame is ready to be transmitted.Detailed description about the adjustment may be found in FIG. 6, FIG.8A and FIG. 8B.

The data transmitting and receiving unit 530 may be configured totransmit and receive data. The data may include data received from thedata compressing and packing module 504 (e.g., a compressed and/orpacked video frame, a compressed and/or packed sub-frame), the storagemodule 508, or other components of the UAV system 100 (e.g., the UAVtransceiver 202, the storage medium 214, etc.), etc. For example, thecompressed and/or packed sub-frame received from the data compressingand packing module 504 may be transmitted by the data transmitting andreceiving unit 530 to the UAV transceiver 202 for processing. Thecompressed and/or packed sub-frame may be transmitted in the physicallayer. The processing may include amplification, analog-to-digitalconversion, digital-to-analog conversion, etc. The UAV transceiver 202may send the processed data to the ground terminal 104. As anotherexample, the data transmitting and receiving unit 530 may obtain datafrom the storage module 508.

The storage module 508 may be configured to store data. The data may beobtained from the data acquisition module 502, the data compressing andpacking module 504, the physical layer processing module 506, and/orother devices. The data may include programs, software, algorithms,functions, files, parameters, text, numbers, images, videos, audios, orthe like, or any combination thereof. In some embodiments, the storagemodule 508 may include a hard disk drive, a solid-state drive, aremovable storage drive (e.g., a flash memory disk drive, an opticaldisk drive, etc.), a digital video recorder, or the like, or acombination thereof.

It should be noted that the above description about the processor 204 ismerely for the purposes of illustration, and is not intended to limitthe scope of the present disclosure. For persons having ordinary skillsin the art, multiple variations and modifications may be made under theteaching of the present disclosure. In some embodiments, the storagemodule 508 may be omitted from the processor 204 and/or incorporatedinto the storage medium 214. However, those variations and modificationsmay not depart from the scope of the present disclosure.

FIG. 6 illustrates a flowchart of an exemplary process 600 fortransmitting a video frame in a UAV system according to some embodimentsof the present disclosure. In some embodiments, the process 600 may beimplemented by the processor 204.

In step 602, video data may be recorded. In some embodiments, step 602may be implemented by the video recording device 206. Step 602 may besimilar to Step 302 of FIG. 3, and is not repeated here.

In step 604, a video frame may be extracted from the video data. In someembodiments, step 604 may be implemented by the data acquisition module502. As used herein, the video frame may refer to a frame of the videodata. The video frame may correspond to a length of time. In someembodiments, the video frame may be a still image.

In step 606, the video frame may be compressed. In some embodiments,step 606 may be implemented by the data compressing and packing module504. The video frame may be segmented into a plurality of sub-frames.Data associated with each of the plurality of sub-frames may becompressed. Each of the plurality of sub-frames may correspond to aportion of the video frame. The video frame may be segmented into aplurality of sub-frames of the same or different lengths. Relateddescription about the compression may be found in the description of thedata compressing and packing module 502.

In step 608, a time period for compressing the video frame may bedetermined. In some embodiments, step 608 may be implemented by thephysical layer processing module 506. The time period for compressingthe video frame may be determined based on the length of the video frameand the compressing algorithms used. In some embodiments, the timeperiod for compressing the video frame may refer to the sum of timeperiods of compressing all the sub-frames of the video frame. In someembodiments, the time period of compressing the video frame in thepresent application may also refer to a time period of compressing asub-frame of the video frame.

In some embodiments, the compressed video frame (or sub-frames thereof)may be further packed in step 606. In this case, the time perioddetermined in step 608 may include the time period for both compressingand packing the video frame (or the sub-frames thereof). In someembodiments, the time period for compressing the video frame may includeother processing time of the video frame before transmission, forexample, the time for adding redundancy check bits to the packed videoframe.

In step 610, a frame header may be extracted from the video frame. Insome embodiments, step 610 may be implemented by the data acquisitionmodule 502. The frame header may include control information of thevideo frame. The control information may include synchronizationinformation, address information, error control information, codinginformation, etc. The synchronization information may include a starttime point and/or an end time point of the video frame.

In step 612, a first time point corresponding to the frame header of thevideo frame may be determined. In some embodiments, step 612 may beimplemented by the physical layer processing module 506. As used herein,the first time point may refer to the start time point of the videoframe. In some embodiments, the frame header of the video frame maycorrespond to a frame synchronization pulse signal. The time point thatthe frame synchronization pulse signal is received at the physical layermay further be determined as the first time point.

In step 614, a second time point may be determined based on the firsttime point obtained in step 612 and the time period for compressing(and/or packing) the video frame obtained in step 608. In someembodiments, step 614 may be implemented by the physical layerprocessing module 506. As used herein, the second time point may referto a time point when the compression and/or packing of the video frameis completed. For example, the second time point may refer to a timepoint that the compression and/or packing of the sub-frame is completed.Detailed description about the determination of the second time pointmay be found in FIG. 8A and FIG. 8B.

In step 616, a third time point corresponding to a frame header of aphysical layer frame may be synchronized with the second time point. Insome embodiments, step 616 may be implemented by the physical layerprocessing module 506. For example, the third time point correspondingto the frame header of the physical layer frame may be synchronized withthe second time point at which the compression and/or packing of thesub-frame is completed. The physical layer frame may control a datatransmission and the frame header of the physical layer frame mayindicate the start of the data transmission. For example, the frameheader of the physical layer frame may indicate the start oftransmission of the compressed and/or packed sub-frame through thephysical layer. The transmission time of a physical layer frame may be afixed value as the length of the physical layer frames may be configuredas the same. In some embodiments, the transmission time of a presentphysical layer frame may be extended or shorten such that the frameheader of the succeeding physical layer frame and the second time point(i.e., the time point at which the compression and/or packing of thesub-frame is completed) are synchronized. In some embodiments, thetransmission time of one or more of the succeeding physical layer framesfrom the present physical layer frame may be adjusted in a similarmanner as transmission time of the present physical layer frame. In someembodiments, only the transmission time of the present physical layerframe is adjusted and by maintaining a certain relationship between theframe rate of the video frame and the physical layer frame, thetransmission time of the succeeding physical layer frames may not needto be adjusted. Alternatively, the transmission time of the presentphysical layer frame may be adjusted each time a video frame is receivedfor compression and transmission.

In some embodiments, the frame synchronization pulse signal indicatingthe time point of receiving the video frame from the video recordingdevice may be transmitted to the physical layer. A snapshot may be takenon the timer of the physical layer to record the occurrence time pointof the frame synchronization pulse signal at the physical layer. Thephysical layer processing module 506 may calculate a start time point oftransmitting the video frame based on the occurrence time point of theframe synchronization pulse signal (i.e., the time point when the videoframe from the video recording device for transmission) and the time forcompressing and/or packing the video frame. The physical layerprocessing module 506 may further compare the calculated start timepoint of transmitting the video frame with a scheduled time point ofgenerating a physical layer frame and determine whether the calculatedstart time point of transmitting the video frame and the next scheduledtime point of generating a physical layer frame are synchronous. When itis determined that the calculated start time point of transmitting thevideo frame and the next scheduled time point of generating a physicallayer frame are asynchronous, the physical layer processing module 506may adjust the value of the physical layer timer such that the nextscheduled time point of generating a physical layer frame is adjusted tobe the same as the calculated start time point of transmitting the videoframe. Detailed description about the synchronization may be disclosedin FIG. 8A and FIG. 8B.

In step 618, the compressed video frame may be transmitted at the thirdtime point. In some embodiments, step 618 may be implemented by thephysical layer processing module 506. For example, the compressed and/orpacked sub-frame may be transmitted at the third time point with thecorresponding physical layer frame in the physical layer. In someembodiments, the compressed and/or packed video frame may be transmittedto a remote device (e.g., the ground terminal 104, the server 108, thestorage 110, etc.) via the UAV transceiver 202.

In step 620, the process 600 may determine whether the transmission ofthe video frame (or the sub-frames thereof) is completed. If thetransmission of the video frame is not completed, the process 600 mayproceed back to step 616. For example, a plurality of third time pointscorresponding to the plurality of the sub-frames may be obtainedrespectively. Each of the plurality of sub-frames may be transmitted atthe corresponding third time point in sequence. The plurality ofsub-frames may be transmitted by repeating step 616 to step 618. If thetransmission of the video frames is completed, the process 600 mayproceed to step 622. In step 622, the processor 204 may wait for nextvideo data. When the next video data is received or recorded, it may beprocessed by the processor 204 by repeating steps 604-620.

It should be noted that the steps as shown in FIG. 6 are forillustrative purpose, and are not intended to limit the protection scopeof the present disclosure. In some embodiments, the process may beaccomplished with one or more additional steps not described, and/orwithout one or more of the steps discussed above. Additionally, theorder that the steps of the process 600 are performed in FIG. 6 is notintended to be limiting. For example, step 606 and step 610 may beperformed simultaneously or successively. As another example, step 614and step 616 may be merged into one step. As another example, step 616may be separated into two steps: a third time point determination and athird time point adjustment. In some embodiments, the video data mayinclude a plurality of video frames. Each of the video frames may beprocessed by repeating steps 604-620.

FIG. 7 illustrates a flowchart of an exemplary process 700 forconfiguring a frame rate of physical layer frames in a UAV systemaccording to some embodiments of the present disclosure. In someembodiments, the exemplary process 700 may be implemented by theprocessor 204.

In step 702, a plurality of video frames may be received. The videoframes may be extracted from the video data recorded in methods similarto those disclosed in step 602 and/or step 302.

In step 704, a frame rate of the plurality of video frames may beobtained. Each of the video frames may be a still image. The frame rateof the plurality of video frames may refer to the number of still imagesobtained per second. For example, the frame rate of twenty video framesmay be obtained by dividing the total time (in seconds) of the twentyframes by twenty.

In step 706, a frame rate of a plurality of physical layer frames may beconfigured based on the frame rate of the plurality of video frames. Theframe rate of the plurality of physical layer frames may refer to thenumber of physical layer frames per unit of time (e.g., second ormillisecond). As described elsewhere in present disclosure, the frameheader of the present physical layer frame may be synchronized withpresent video frame to reduce wait time and delay. In step 706, theframe rate of the physical layer frames may be configured so that thesubsequent physical layer frames may be synchronized with the subsequentvideo frames, respectively. More particularly, the frame rate ofphysical layer frames may be adjusted such that each frame header of thephysical layer frames is synchronized or almost synchronized with thetime point when the compression of the video frame is completed. In someembodiments, the frame rate of the plurality of physical layer framesmay be an integer multiple of the frame rate of the plurality of videoframes. Merely by way of example, the integer may be 2, 4, 6, 8, 10, 20,25, 30, etc.

It should be noted that the steps as shown in FIG. 7 are forillustrative purpose, but are not intended to limit the protection scopeof the present disclosure. In some embodiments, the process may beaccomplished with one or more additional steps not described, and/orwithout one or more of the steps discussed above. Additionally, theorder in which the steps of the process as illustrated in FIG. 7 is notintended to be limiting.

FIG. 8A and FIG. 8B illustrate two schematic diagrams of a videotransmission in a UAV system according to some embodiments of thepresent disclosure. In some embodiments, FIG. 8A and FIG. 8B illustratea video transmission from the UAV 102 to the ground terminal 104.

In some embodiments, as illustrated in FIG. 8A and FIG. 8B, the videotransmission may include capturing video data via the UAV 102, receivingvideo frames at the UAV 102, compressing the video frames at the UAV102, processing the video frames at the UAV 102, transmitting the videoframes via at the UAV 102 according to the timings of the physical layerframes, transmitting the video frames from the UAV 102 to the groundterminal 104 wirelessly, receiving and decompressing the video frames inthe ground terminal 104, etc. A plurality of video frames may beextracted from a real-time video. The plurality of video frames mayinclude a video frame 802-1, a video frame 802-2, etc. In someembodiments, the real-time video may be received at a data interface(e.g., a universal serial bus (USB) interface, an IEEE1394 interface, ora RS-232 interface, etc.) communicatively connected to a camera (e.g.,the video recording device 206). A frame timing of the camera mayinclude a plurality of signals that indicate the start time points ofthe camera to record videos. The plurality of signals may include asignal 800-1, a signal 800-2, a signal 800-3, etc. The video frame 802-1and the video frame 802-2 may be segmented into sub-frames andcompressed into a plurality of compression packages, including acompression package 804-1, a compression package 804-2 . . . acompression package 804-7, etc. The segmentation and compression methodmay be similar to the description of data compressing and packing module504. The plurality of compression packages may be transmitted throughphysical layer under the control of a plurality of physical layer framesincluding a physical layer frame 806-1, a physical layer frame 806-2 . .. a physical layer frame 806-8, etc. The plurality of compressionpackages corresponding to the video frames may be received in the groundterminal 104 and may be decompressed as a plurality of decompressedvideo frames, including a decompressed video frame 808-1, a decompressedvideo frame 808-2 . . . a decompressed video frame 808-5, etc.

As illustrated in FIG. 8A, a time point T1 may correspond to the frameheader of the video frame 802-1. A time point T4 may correspond to thetime point when the compression package 804-1 is received anddecompressed (the decompressed video frame that correspond to thecompression package 804-1 is denoted by 808-1). A time period t3 maycorrespond to the time period for compressing and/or packing the firstsub-frame of the video frame 802-1. A time point T2 may be determinedbased on the time point T1 and the time period t3. The time point T2 mayindicate that the compression package 804-1 is compressed and ready tobe transmitted. However, the time point T2 is not synchronized with thetime point T3 corresponding to the frame header of the physical layerframe 806-2 (shown as the time point T9). Hence, the compression package804-1 cannot be transmitted until at a time point corresponding to theframe header of the physical layer frame 806-3 (shown as the time pointT3). A wait time period t2 may be defined as the time length that thecompression package 804-1 needs to wait before it is transmitted. A timedelay may be defined as a time period from the start time of the videoframe to the time point when the video frame is available for streamingand/or playback at the ground terminal 104. As shown in FIG. 8A, a timedelay t1 may refer to a time period from the time point T1 to the timepoint T4, which may be unnecessarily extended due to the wait timeperiod t2. The method disclosed in present disclosure may be implementedto eliminate or reduce the wait time, hence to reduce the time delay.

FIG. 8B illustrates a schematic diagram of a video transmission similarto FIG. 8A but with adjusted physical layer frame timings. Asillustrated in FIG. 8B, a time point T5 may correspond to the frameheader of the video frame 802-1. A time point T8 may correspond to thetime point when the compression package 804-1 is received anddecompressed (the decompressed video frame that correspond to thecompression package 804-1 is denoted by 808-1). A time period t5 maycorrespond to the time period for compressing and/or packing the firstsub-frame of the video frame 802-1. A time point T7 may be determinedbased on the time point T5 and the time period t5. The time point T7 mayindicate that the compression package 804-1 is compressed and ready tobe transmitted. A time point T6 may correspond to the frame header ofthe physical layer frame 806-1. To synchronize the time pointcorresponding to the frame header of the physical layer frame 806-2, thephysical layer frame 806-1 may be adjusted. For example, the length ofphysical layer frame 806-1 may be extended. As another example, aninternal reading of a timer that corresponds to the frame header of thephysical layer frame 806-1 may be increased. In particular, the readingof the timer may be adjusted such that the time point corresponding tothe frame header of the physical layer frame 806-2 is synchronized withthe time point T7. The transmission time of the physical layer frame806-1 may be extended or shorten so that the time point corresponding tothe frame header of the physical layer frame 806-2 is synchronized withthe time point T7. A time delay t4 may be defined as a time period fromthe time point T5 to the time point T8. With the timing adjustment ofthe physical layer frame 806-1, the compression package 804-1 can betransmitted immediately when the compression is completed, i.e., withoutthe wait time period t2 as shown in FIG. 8A. In some embodiments, onlythe transmission time of the physical layer frame 806-1 is adjusted andthe transmission time of the physical layer frame 806-2 and thesubsequent physical layer frames are not adjusted until a subsequentvideo frame is received.

In some embodiments, as illustrated in FIG. 8B, each of the plurality ofvideo frames may be transmitted with the timing adjustment of a numberof physical layer frames. The number of physical layer frames of whichthe timings need to be adjusted may be relevant with a frame rate of theplurality of physical layer frames and a frame rate of the plurality ofvideo frames. In some embodiments, the frame rate of the plurality ofphysical layer frames may be configured to be an integer multiple (e.g.,twenty) of the frame rate of the plurality of video frames so that thenumber of physical layer frames of which the timings need to be adjustedmay be greatly decreased.

FIG. 9 illustrates a schematic diagram of an exemplary OSI model. TheOSI model 900 characterizes and standardizes the communication functionsof a telecommunication or computing system. The OSI model 900 defines anetworking framework to implement protocols in seven layers. From thebottom up, the seven layers may include a physical layer 902, a datalink layer 904, a network layer 906, a transport layer 908, a sessionlayer 910, a presentation layer 912, and an application layer 914.

The physical layer 902 defines electrical and physical specifications ofa data connection. The physical layer 902 defines the relationshipbetween a device and a physical transmission medium (e.g., a copper orfiber optical cable, a radio frequency, etc.). The relationship mayinclude layout of pins, voltages, line impedance, cable specifications,signal timing and similar characteristics of connected devices,frequency (5 GHz or 2.4 GHz etc.) of wireless devices, etc. The physicallayer 902 may convey a bit stream (e.g., an electrical impulse, light orradio signals, etc.) through network at the electrical and mechanicallevel. The physical layer 902 may provide hardware means of sending andreceiving data on a carrier, including defining cables, cards andphysical aspects. In some embodiments, the physical layer processingmodule 506 and/or the user interface 408 may operate in the physicallayer 902.

The data link layer 904 may furnish transmission protocol knowledge,management, handling errors in the physical layer 902, flow control,frame synchronization, etc. In the data link layer 904, data packets maybe encoded and decoded into bits. In some embodiments, the data linklayer 904 may be divided into two sub layers: the Media Access Control(MAC) layer and the Logical Link Control (LLC) layer. The MAC sub layermay control how a computer on the network gains access to data andpermission to transmit the data. The LLC layer may control framesynchronization, flow control and error checking. In some embodiments,the processor 204, the processor 404 of the UAV system 100 may operatein the data link layer 904.

The network layer 906 may provide switching and routing technologies,and creating logical paths for transmitting data from node to node. Insome embodiments, the network 106, the UAV transceiver 202, and/or theground terminal transceiver 402 may operate in the network layer 906. Insome embodiments, accessing of the UAV 102 to the network 106 may beoperated in the network layer 906. The access may be a competition-basedrandom access or a non-competition-based random access.

The transport layer 908 may provide transparent transfer of data betweenend systems, or hosts. The transport layer 908 may be responsible forend-to-end error recovery and flow control. The transport layer 908 mayensure complete data transfer. In some embodiments, the network 106, theUAV transceiver 202, and/or the ground terminal transceiver 402 mayoperate in the transport layer 908. In some embodiments, protocols thatoperate in the transport layer 908 may include TCP, UDP, SPX, etc.

The session layer 910 may control connections between devices. Thesession layer 910 may establish, manage and terminate the connectionsbetween devices. In some embodiments, the processor 204 and/or theprocessor 404 may operate in the session layer 910.

The presentation layer 912 may provide independence from differences indata representation (e.g., encryption) by translating from applicationto network format, and vice versa. The presentation layer 912 may workto transform data into the form that the application layer 914 canaccept. In some embodiments, the data compressing and packing module 504may operate in the presentation layer 912.

The application layer 914 may provide application services, such as filetransfers, e-mail, or other network software services, etc. Theapplication layer 914 may perform functions including identifyingcommunication partners, determining resource availability, etc. In someembodiments, protocols that operate in the application layer 912 mayinclude FTP, HTTP, DNS, etc.

It should be noted that the OSI model 900 is provided merely for thepurposes of illustration, and is not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations or modifications may be made under the teachings ofthe present disclosure. For example, a device or module of the UAVsystem 100 may work in multiple layers simultaneously or subsequently.However, those variations and modifications may not depart from thescope of the present disclosure.

Having thus described the basic concepts, it may be rather apparent tothose skilled in the art after reading this detailed disclosure that theforegoing detailed disclosure is intended to be presented by way ofexample only and is not limiting. Various alterations, improvements, andmodifications may occur and are intended to those skilled in the art,though not expressly stated herein. These alterations, improvements, andmodifications are intended to be suggested by this disclosure, and arewithin the spirit and scope of the exemplary embodiments of thisdisclosure.

Moreover, certain terminology has been used to describe embodiments ofthe present disclosure. For example, the terms “one embodiment,” “anembodiment,” and/or “some embodiments” mean that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the present disclosure.

Further, it will be appreciated by one skilled in the art that aspectsof the present disclosure may be illustrated and described herein in anyof a number of patentable classes or context including any new anduseful process, machine, manufacture, or composition of matter, or anynew and useful improvement thereof. Accordingly, aspects of the presentdisclosure may be implemented entirely hardware, entirely software(including firmware, resident software, micro-code, etc.) or combiningsoftware and hardware implementation that may all generally be referredto herein as a “block,” “module,” “engine,” “unit,” “component,” or“system.” Furthermore, aspects of the present disclosure may take theform of a computer program product embodied in one or more computerreadable media having computer readable program code embodied thereon.

I claim:
 1. A method implemented on a computing device including atleast one processor and a storage for synchronizing video transmissionwith physical layer, the method comprising: determining a first timepoint corresponding to a frame header of a video frame, the video frameincluding a plurality of sub-frames; determining a time period forcompressing a sub-frame of the plurality of sub-frames according to alength of the sub-frame and a compression algorithm used for compressionthe sub-frame; determining a second time point based on the first timepoint and the time period for compressing the sub-frame; adjusting athird time point corresponding to a frame header of a physical layerframe to synchronize the third time point with the second time point;and starting transmitting the sub-frame at the second time point.
 2. Themethod of claim 1, further comprising: generating the physical layerframe at the second time point.
 3. The method of claim 1, furthercomprising: compressing the sub-frame before transmitting the sub-frameat the second time point.
 4. The method of claim 1, wherein the frameheader of the video frame corresponds to a frame synchronization pulsesignal.
 5. The method of claim 1, wherein the video frame is extractedfrom a real-time video stream transmitted by a video recording device.6. The method of claim 1, wherein the video frame is extracted from areal-time video received at a data interface communicatively connectedto a video recording device.
 7. The method of claim 1, furthercomprising: obtaining a frame rate of the video frame; and configuring aframe rate of the physical layer frame based on the frame rate of thevideo frame.
 8. The method of claim 7, wherein the frame rate of thephysical layer frame is an integer multiple of the frame rate of thevideo frame.
 9. A system for synchronizing video transmission withphysical layer, the system comprising: a memory that stores one or morecomputer-executable instructions; and one or more processors configuredto communicate with the memory, wherein when executing the one or morecomputer-executable instructions, the one or more processors aredirected to: determine a first time point corresponding to a frameheader of a video frame, the video frame including a plurality ofsub-frames; determine a time period for compressing a sub-frame of theplurality of sub-frames according to a length of the sub-frame and acompression algorithm used for compression the sub-frame; determine asecond time point based on the first time point and the time period forcompressing the sub-frame; adjust a third time point corresponding to aframe header of a physical layer frame to synchronize the third timepoint with the second time point; and start transmitting the sub-frameat the second time point.
 10. The system of claim 9, wherein the one ormore processors are further directed to: generate the physical layerframe at the second time point.
 11. The system of claim 9, wherein theone or more processors are further directed to: compress the sub-framebefore transmitting the sub-frame at the second time point.
 12. Anon-transitory computer readable medium including executableinstructions that, when executed by at least one processor, cause the atleast one processor to effectuate a method comprising: determining afirst time point corresponding to a frame header of a video frame, thevideo frame including a plurality of sub-frames; determining a timeperiod for compressing a sub-frame of the plurality of sub-framesaccording to a length of the sub-frame and a compression algorithm usedfor compression the sub-frame; determining a second time point based onthe first time point and the time period for compressing the sub-frame;adjusting a third time point corresponding to a frame header of aphysical layer frame to synchronize the third time point with the secondtime point; and starting transmitting the sub-frame at the second timepoint.